Process and apparatus for analyzing gas



Feb. 1, 1938.v L. L. VAYDA 2,106y777 PROCESS AND APPARATUS FOR ANALYZING GAS Filbd April 26, 1934 IN VEN TOR Lou/5 L. VH rc2/ BY 44 46 yATTORNEY;

Patented Feb. 1, 1938 UNITED STATES ATEN'E` OFFlCE Louis L. Vayda,Aspinwall, Pa.

Application April 26, 1934, Serial No. 722,491

Claims.

|The invention relates to a process and apparatus for analyzing gas. Theobjects of the invention are the provision of a process and apy paratus,which have a very wide eld of use and which permit the analysis ofpractically all kinds of gas for which' there is an industrialrequirement, such as the determination of CO2, CO, Oz, H2, CHi, etc. Afurther object is the provision of an apparatus which is dependable andaccurate; which is easily operable; and which is relatively cheap andsimple in construction.

The invention involves the use of a closed system, to which a gasmixture containing a constituent (or constituents) whose percentage isto be determined, is supplied continuously. Provision is made in thesystem for reacting the constituent with another gas or gases, or forabsorbing it, thus causing a change in the volume of the gas which isproportional to the amount of constituent. At the same time, a volume ofgas is continuously evacuated from the system of such amount that thepressure in the system is maintained constant. Under these conditions,the Volume of the gas supplied to the system, as compared with the gasevacuated, will give a measure or indication of the percentage of theconstituent. In practice, two sets of pumping means are employed, one ofwhich supplies the gas to the system, and the other of which evacuatesit. The displacement of one of these devices may be varied so that, dueto such variation, the pressure in the system may be maintainedconstant. The variation in displacement of the variable pumping means isautomatically regulated by the pressure in the system, and an indicatorregisters the variation in the pump displacement, so that by a suitablecalibration of the indicator, a reading may be had showing thepercentage of the constituent whose reaction or absorption in the systemis responsible for the variation in the pump displacement.

In some cases, the constituent to be removed may be merely removed bycirculating the gas containing the constituent through a suitablecondenser or absorbent. In other cases, the constituent may be of suchcharacter that it will react with some other element in the mixture whenexposed to suilicient heat and/or by the action of a catalyzing agent;and to provide for this type of reaction, the system is supplied with aheating and/or catalyzing chamber through which the gas passes. In othercases, two gases may be supplied to the system by independent pumps, onegas containing the constituent to be determined, and the other being ofa character (Cl. .Z3-255) which will react with the constituent when themixture is passed through the heating chamber. In other cases, the stepsof reaction under heat and subsequent absorption or condensation arenecessary in order to secure a suicient change in volume to give thenecessary determination. The invention will be readily understood from aconsideration of the detailed description following in connection withthe drawing, wherein:

Figure 1 is a diagrammatic View partly in section showing the movingparts in one position. Fig. 2 is a similar View of a part of theapparatus with the moving parts in another position. And Fig. 3 shows amodification.

Referring to the drawing, I and 2 are a pair of cylinders mounted forreciprocation, and provided with the ports 3, 4 and 5, 6; and-I and 8are a pair of pistons working in the cylinders and provided with thepiston rods 9 and IIJ (the latter hollow) connected to the common crosshead II. This cro-ss head is driven from an electric motor I2 throughthe intermediary of the crank I3 and connecting rod I4, current beingsupplied for operating the motor from the leads I5 and I6. Back of thepiston l is a follower I'I which has a rod I8 extending through thehollow piston rod I0 and provided with the threaded portion I9 which isthreaded through the hub of the spur gear 20. The outer end of the rodI8 has a square portion 2| slidable through a xed block 22, so that therod can not turn. It follows that when the gear 20 is rotated, it isadjusted longitudinally of the rod I8, thus adjusting the follower IItoward and from the piston l when these parts are moving in onedirection. It will be apparent that the piston 'I with the follower I1together constitute a plunger which is adjustable as to length anddisplacement when these parts move in one direction, and which comesinto play, as later explained, in maintaining the constant pressure inthe system as heretofore referred to.

The position of the follower is adjusted by the back and forth rotationof the long pinion 23.

which meshes with the gear 20 and is rotated by the shaft 24 of thesplit eld motor 25. When the motor rotates in one direction, the gear 20is adjusted along the rod I8 to the left, so that the space between thepiston I and follower I1 is increased. As a result of this adjustment,the intake of the cylinder I at its right hand end, as the followermoves to the left, is decreased. When the mo-tor rotates in the otherdirection, the gear 2E! is adjusted along the rod I8 to the right, sothat the space between the piston and follower is decreased. As a resultof this adjustment, the intake of the cylinder at its right hand end, asthe follower moves to the left, is increased. The direction of rotationof the split eld motor is controlled by the pressure in the box 26(connected to the closed system) which box has a flexible diaphragm 21connected with the Switch arm 28 having the contact 28 adapted to engageeither the contact 30 or the contact 3l, depending on the pressure inthe closed system and box 26. If the pressure in the system rises abovea certain point, such as atmospheric pressure, the contact 29 isdepressed, so that it engages the contact 3l, and the motor 25 rotatesin one direction, due to the flow of current through the wire 33, arm28, contact 3I, wire 34, one of the motor fields and wire 32. On theother hand, if the pressure in the system drops below said point, thecontact 29 is raised, so that it engages the contact 30, and the motorrotates in the reverse direction, due to thel flow of current throughthe wire 33, arm 28, contact 30, Wire 35, the other motor field coil andthe wire 32.

The relative position of the piston 1 and the follower I1 is indicatedby means of the pointer 36 working over the scale 31 and having its basethreaded onto the extended end of the shaft 24, the pointer beingsuitably guided and held against a movement of rotation with the screw.This pointer is moved back and forth depending upon the direction ofrotation of the motor 25, and its position is determined by the angulartravel of the motor shaft, which in turn corresponds with the adjustmentof the follower I1, so that, if the pressure in the system is maintainedconstant, the position of the pointer is a gauge of the changes involume of gas delivered to the system in order'to maintain its constantpressure. By suitable calibration, the pointer can be made to indicatethe extent of the reactions occurring in the system. A recording drum 38may be located below the pointer, and such pointer provided with arecording pen 39 for making a record of the position of the pointerthroughout the period of operation.

A gas to be analyzed, such as flue or exhaust gas from the combustion offuel, is supplied to the cylinder I through the pipe 40, While a secondgas, such as air, is supplied to the cylinder 2 through the pipe 4I. Ifdesired, the air may be supplied through the pipe 40, and the gas to betested through the pipe 4 I. The two cylinders discharge to a closedsystem which includes the pipes 42 and 43 and the furnace 44 through thepassage 45 when the parts` are in the position of Fig. 2 with the ports3 and 6 in registration with such passage. The furnace 44 is heated fromthe coil 46 supplied with electric current from the leads I5 and I6. Thepipe 43 is connected with the box 26 which acts as one of the elementsin maintaining a constant pressure in the system as heretofore referredto. The pipe 43 is connected by means of a pipe 41 with a passage 48which communicates at its ends with the ports 4 and 5 when the parts arein the position of Fig. 2. 50 is an exhaust passage to the atmospherewhich registers with the ports 4 and 5 when the parts are in theposition of Fig. 1.

The cylinders I and 2 are mounted for sliding movement from the extremeposition, as indicated in Fig. 1, to the other extreme position, asindicated in Fig. 2, and their movement from one position to the otheroccurs when the plunger 1, I1 and piston 8 approach the ends of theirstrokes and engage the cylinder heads. In their movement to the right,the piston 1 engages the follower I1 and they move together. Thecylinders are pressed yieldingly against the surfaces on which theyslide by any suitable means, which in the present instance, arediagrammatically shown as plates 5I and 52 engaging the outer sides ofthe cylinders and pressed inward by the springs 53 and 54.

Starting with the parts in the position of Fig. 2 and the pistons movingto the right, the piston 8 and follower l1 are forcing into the pipe 42the gases in the cylinders to the right of the pistons via the ports 3and 6 and the passage 45. At the same time, a volume of gas is beingevacuated from the pipe 41 into the cylinders to the left of the pistonsvia the passage 48 and the ports 4 and 5, This causes a circulation ofgas through the pipe 42, furnace 44, 4and pipe 43 giving opportunity fora reaction to occur in the furnace resulting in a change in volume. Thesupply of gas to the pipe 42 and withdrawal through the pipe 41continues until the pistons reach the right hand ends of the cylinders,where they engage the cylinder heads and move the cylinders to theposition of Fig. 1. This brings the ports 3 and 6 into registration withthe passages 55 and 5S respectively, with which the pipes 40 and 4Icommunicate, and as the pistons move to the left,

the cylinders are lled with gas from the pipes.

It is to be noted that the follower I1 will remain stationary until theupper part of the cross head I I strikes the gear 2o, after ,Which thefollower I1 will follow the piston I1 drawing into the cylinder .areduced volume of gas, as previously described. With the cylinders inthe position of Fig. 1, the ports 4 and 5 are in registration with theexhaust passage 59, so that as the pistons move to the left, thecontents of the cylinders to the left of the pistons is discharged tothe atmosphere. This intake of gas into the right hand end of thecylinders, andthe exhaust of the left hand ends continues until thepistons engage the heads at the left hand ends of the cylinders, whensuch cylinders are shifted to the left to the position of Fig. 2. Thepistons 1 and 8 now start to the right, the piston 1 shortly engagingthe follower I1 and bringing the parts back to the starting position ofthe cycle as above outlined.

In the above operation, the reaction in the furnace 44 transforms the COin the flue gas to CO2 and the hydrogen H2O as shown by the followingequation:

From which it is seen that three volumes of the reacting gases in eithercase give two volumes of gaseous products of reaction. It follows,therefore, that if the amount of gas withdrawn from the system equalsthat supplied thereto, a drop in pressure occurs. If now the intakerelative to the outgo is adjusted, so as to maintain the pressureconstant, a measure of this diiference in volume taken into the system,as compared with that exhausted, will give an index of the amount ofcombustible which reacted in the furnace.

Assuming that, with the apparatus adjusted as shown in the drawing, withthe follower 1 spaced away from the piston 1, the intake of theapparatus is equal to its outgo and that there is no reaction in thesystem tending to change the Volume of the gas, the switch arm' 28 willb-e in middle position and the pointer 3S Will be at the zero point. Ifnow, the reaction occurs in the system as set forth in the precedingparagraph, causing a reduction inthe ypressurezinthe system, thediaphragm 21 .willmove 4down .causing the contact 29to engage thecontact 3l). The motor shaft 24 is now rrotated, rotating the .gears 23and 20, and moving the gear20 `along the rod I8 to the right. On themovement'of v`the 4cross head and the piston 1 to the left, therefore,Athe follower is closer to the piston than before. The adjustment thusincreases the intake capacity of the follower, but Without changing theevacuating capacity of the piston 1, since on the;move ment of. thepiston and Ifollower .to Vthe right, such parts engage, as indicated inFig. 2. The volume of gas pumped into thesystem will thus be .increased,and Athis increase vwill'continue until :the pressure built up yin `thesystem is sufficient to compensate forvthe loss in volume-due tothereaction in the furnace 44. At such time, `the diaphragm will bemoved-upto its original neutral position, so as to separate the contacts29 and 30. The variation inthe position of the follower will beregistered by the pointer 36, since the `movement produced in the shaftI8 by the motor shaft 24 is duplicated in the pointer on a larger scale.

`If during the analysis, the pressure increases, the

diaphragm 21 is moved up, causing vthe contact 29 to engage the contact3|,1which vresults in a rotation of the motor 25 in a direction thereverse of its previous .movement This `causes a movement of the shaftI8 and follower I.1 to the right, thus decreasing the intake capacity ofthe follower I1, so that the pressure in the vsystem drops and thecontact between 29 and 3l is broken, stopping the motor 25. 'I'hemovement ofthe follower tothe right as just described, :is accompaniedby a corresponding movement of the pointer 36 to the right. Since thechange in volume of the gas in the system reflects the' extent of thereaction of the gases in the furnace 44, it follows that the change indisplacement in the follower I1 in order lto maintain a constantpressure in the system is a correct indication of the amount of theconstituent in the gas subject to the reaction.

In the operation, as above described, it is necessary in order to getaccurate results, to maintain the cylinders, connecting passages andtubing at a temperature high enough to prevent condensation of the watervapor formed .by the reacting gases. This can easily be accomplished byplacing the apparatus in a heated cabinet (not shown) or by submergingit in a heated liquid, such as oil, which latter expedient has thefurther advantage of lubricating the moving parts.

A further application of the .apparatus is in the determination of. thepercentage of oxygen in the flue and furnace gases from boiler furnaces,industrial heating and annealing furnaces, open hearth furnaces, kilns,etc. In using the apparatus, the cylinder I is connected so as to drawin the gas to be analyzed, while the cylinder 2 is connected to draw ina gas which will unite with the oxygen, such as hydrogen. The reactionin the furnace is indicated by the following equation:

From which it is seen that three volumes of the reacting .gases give twovolumes of the gaseous products of the reaction, resulting in a changeof pressure in the system, as heretofore described. The use of theapparatus also requires a maintenance of the temperature of theapparatus above a given point to prevent condensation, and

suitable means may be employed for the purpose, as above described.

To determine the percentage of absorbable constituent, or constituents,in a gas mixture, such as for instance, the percentage of CO2 in furnaceand lflue gases from boiler furnaces, etc. as well asin exhaust gasesfrom internal `combustion engines, the furnace 44 need not be employed,and an absorbing unit, as indicated at 51, is used, such unit vbeingsupplied with potassium hydroxide which will remove the carbon dioxide.This unit is connected to the pipe v43 by the pipes 58 and 59 carryingthe valves 60 and 6I. In using the unit, the valves 69 and 6I are openedand the valve 62 is closed, so that `the .gases to be acted vupon arecirculated through the casing 51. The coil 46 in the furnace 4'4, duringvthis operation, is not heated. Under these conditions, the CO2 in thegas is completely absorbed in the unit 51, thus reducing the pressure inthe system, and causing a shift in the position of the follower I1 sothat its lag with respect to the piston 1 is reduced with acorresponding movement of the pointer 3B. In this case, the scale 31 andchart 38 are calibrated directly in terms of percentage of theabsorbable constituent or constituents, by volume in the original gas.In this and similar cases in which the same gas is admitted through bothpipes 40 and 4I, the cylinder I would be used for the gas, and the useof the cylinder 2 and piston 8 is, of course, superfluous as theymer-ely add to the volume of the gas tested, the device being calibratedto meet this condition.

The apparatus may further be used to determine the percentage of carbonmonoxide and/or hydrogen in air, such as may exist in vehicular tunnels,garages, or other confined spaces subject to pollution by the exhaustgases from automotive vehicles. In this case, as in the preceding one,the air to be tested is drawn into the system through both pipes 4'0 and4I, the oxygen in the mixture being suiiicient to give the necessaryreaction in the furnace 44. The reaction is indicated by the followingequations:

acting gases in either case give two volumes of l gaseous products ofreaction. But since the percentage by volume of carbon monoxide and/orhydrogen in the air tested, will in most cases be small, the volumechange due to the reaction will be correspondingly small, perhaps toosmall for c practical measurement of the resulting change in intakedisplacement and stroke of the follower I1. It is, therefore, desirableto increase the difference in volume, and this is accomplished by theuse of the unit 51 heretofore described. The unit may be equipped toremove the carbon dioxide formed, as by the use of potassium hydroxide,and/or for the removal of the water vapor by the use of calciumchloride. As before, the unit 51 is brought into use by opening thevalves 60 and through pipes 40 and 4|, and the unit 51 is utilized. Inthis case, the reaction is indicated by the following equation:

It will be seen that three volumes of the reacting gases gives threevolumes of the gaseous products of the reaction. There is thus no changein Volume. 'Ihe necessary change in volume is secured by passing thegases through the unit 51, which as before, is requipped to chemicallyremove the carbon dioxide by the use of potassium hydroxide, and thewater vapor by the use of calcium chloride. reacting gases may thus beremoved, and the resulting variation in volume in the system measured.

Fig. 3 illustrates a modified means for holding the cylinders againsttheir seats and maintaining them yieldingly in the extremes of movementuntil positively moved by the pistons. The cylinder is provided on itsupper si'de with two recesses 63 and 64 adapted to be engaged by theroller 65 on the arm 66 yieldingly pressed down by the spring 61, thearm 66 being pivoted to the fixed bracket 68. The cylinder is held inthe position shown until the piston l, which is moving to the left,engages the end of the cylinder and moves it to the left. The roller 65resists this movement, but is cammed upward and then moves down andengages the recess 64 holding the cylinder in its new position until thereverse movement of the piston 'I shifts the cylinder back to theposition shown.

It will be understood that the apparatus is illustrated in a very simpleform, and is capable of wide modification and elaboration. Various otherforms of pumps may be employed for carrying out the process. Thereaction of the gases is preferably accomplished by the application ofheat, as supplied by the furnace M, but other means may be employed forpromoting the reaction, including a catalyzing agent with or withoutheat, such as palladium sponge or certain metallic oxides well known inthe art. While the electric switch means operated by pressure andincluding the motor 25 are preferably used for maintaining the constantpressure in the system, the invention is not limited to the use of thisparticular device, as mechanically operated means might be substituted.As shown and described, the pressure in the system is maintainedconstant by varying the intake, but it will be understood that thisresult may equally well be accomplished by varying the amount of gasexhausted, and that the claims are, with respect to this feature, to beconstrued broadly in accordance with their terms.

What I claim is:

1. Apparatus for analyzing a gas comprising a closed testing system, acollateral sampling system, means for pumping into the testing system agas mixture containing a constituent whose percentage it is desired todetermine, means in the testing system for treating the mixture so thatits volume is modiiied to an extent dependent upon the amount of saidconstituent, means for evacuating from the testing system a volume ofthe treated gas, said means for delivering the gas and evacuating itcomprising the sampling system including a cylinder, a piston workingtherein, a follower for the piston which in. the

movement of the piston in one direction engages such piston and in themovement of the piston in the other direction is held spaced away there-The volume of the from, a port at one end of the cylinder for receivingthe gas to be analyzed as the piston and follower move away from theport, connections whereby such gas is forced into the testing system onthe reverse movement of the piston, a port at the other end of thecylinder for receiving the gas to be evacuated from the testing systemas the piston and follower move away from such last port, connectionswhereby such last mentioned gas is forced from the sampling system intothe atmosphere on the reverse movement of the piston, and means forindicating the degree of separation of the piston and its follower.

2. Apparatus for analyzing a gas comprising a closed testing system, acollateral sampling system, means for pumping into the testing system agas mixture containing a constituent whose percentage it is desired todetermine, means in the testing system for treating the mixture so thatits volume is modified to an extent dependent upon the amount of saidconstituent, means for evacuating from the testing system a volume ofthe treated gas, said means for delivering the gas and evacuating itcomprising the sampling system including a cylinder, a piston workingtherein, a follower for the piston which in the movement of the pistonin one direction engages such piston and in the movement of the pistonin the other direction is held spaced away therefrom, a port at one endof the cylinder for receiving the gas to be analyzed as the piston andfollower move away from the port, connections whereby such gas is forcedinto the testing system on the reverse movement of the piston, a port atthe other end of the cylinder for receiving the gas to be evacuated fromthe testing system as the piston and follower move away from such lastport, connections whereby such last mentioned gas is forced from thesampling system into the atmosphere on the reverse movement of thepiston, means governed by the pressure in the testing system forregulating a degree of separation to the piston and its follower, andmeans for indicating the degree of separation-of the piston and itsfollower.

3. A method of analyzing gas, which consists in pumping separately intoa sampling system a gas mixture containing a constituent, the percentageof which it is desired to determine, and a fixed proportion of someother gas which will react with the constituent in a denite manner sothat the volume of the gaseous products of the reaction is differentfrom the initial volume of the reacting gases, pumping said mixture intoa closed testing system, causing said reaction to occur, pumping fromthe sampling system, coincident with the supply of gas thereto, aquantity of the gaseous products of the reaction, varying the relativevolumes of gas delivered into and removed from. the testing system sothat the pressure in the testing system is maintained constant, andduring the pumping of gas into and out of the sampling system, measuringthe difference between the volume of gas delivered to the testing systemand'that withdrawn therefrom to give a determination of saidconstituent.

4. Apparatus for analyzing gas containing a constituent whose percentageit is desired to determine, comprising a closed testing system, acollateral sampling system, means for pumping into and at the same timepumping from the sampling system a gas mixture, means in the closedtesting system for treating the mixture so that its volume is modieddependent upon the amount of said constituent, said means for deliveringthe gas and exhausting it comprising a cylinder provided with a drivenplunger and a driven follower, one end of the cylinder receiving the gasto be supplied to the sampling system as the plunger, and follower movein one direction and supplying it to the testing system on the reversestroke, and the other end of the cylinder receiving the gas from thetesting system as the plunger and follower move in one direction anddischarging it to the atmosphere on the reverse stroke, said plungerhaving a constant displacement and the follower being adjustable as todisplacement and means for indieating the variable displacement of thefollower during the pumping operation.

5. Apparatus for analyzing gas containing a constituent whose percentageit is desired to determine, comprising a closed testing system, acollateral sampling system, means for pumping into and at the same timepumping from the sampling system a gas mixture, means in the closedtesting system for treating the mixture so that its volume is modieddepending upon the amount of said constituent, said means for deliveringthe gas and exhausting it comprising a cylinder provided with a drivenplunger and a driven follower, one end of the cylinder receiving the gasto be supplied yto the sampling sys'- tem as the plunger and followermove in one direction and supplying it to the testing system on thereverse stroke, and the other end of the cylinder receiving the gas fromthe testing system as the plunger and follower move in one direction anddischarging it to the atmosphere on the reverse stroke, said plungerhaving -a constant displacement and the follower being adjustable as todisplacement, means governed by the pressure in the testing system forregulating the displacement of the follower so that such pressure ismaintained constant and means for indicating the variable displacementof the follower during the pumping operation.

LOUIS L. VAYDA.

